Heat exchange technique

ABSTRACT

A method and device that transfers heat to or from a gas. The method includes the steps of moving a surface with sufficient speed to disrupt a velocity boundary layer for molecules of the gas in contact with the surface, and cooling or heating the surface. The surface can be a heteroscopic structure that selects molecules from the gas. Cooling results in a transfer of energy from the molecules to the surface, whereas heating results in a transfer of energy from the surface to the molecules.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Provisional Application No.60/434852, “Air Flow, Heat Exchange, and Molecular Selection Systems,”filed Dec. 19, 2002, in the name of inventors Scott Davis and ArtWilliams; from Provisional Application No. 60/499,066, “Molecular SpeedSelection, Flow Generation, Adiabatic Cooling, and Other HeteroscopicTechnologies,” filed Aug. 29, 2003, in the name of inventors Scott Davisand Art Williams; from U.S. patent application No. Ser. 10/693,635,“Heteroscopic Turbine,” filed Oct. 24, 2003, in the name of inventorScott Davis; and from U.S. patent application No. Ser. ______,“Molecular Speed and Direction Selection,” filed Dec. 16, 2003, in thename of inventor Scott Davis, Express Mail Label No. EL 768 962 519 US.These applications are incorporated by reference as if fully set forthherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to exchanging heat with a gas. In particular, theinvention relates to transferring heat to or from the gas, for examplethrough forced conduction.

2. Description of the Related Art

One prevalent device in modern technology is a device that exchangesheat with air or other gaseous matter. Examples of such devices includecooling units for computers, radiators for cars, air conditioners,refrigerators, heaters, industrial cooling units for large machinery,and innumerable other devices.

Prior art techniques for exchanging heat with air involve forcedconvection. In forced convention, air is forced to flow over or throughsome heating or cooling element. For example, air can be blown over orthrough a heated or cooled substrate, duct or grille. The purpose ofthese arrangements can be to heat or cool either the air or thesubstrate, duct or grille.

In all of these prior art arrangements, a boundary layer forms over thesurface of the substrate, duct or grille. In particular, air moleculesin contact with the surface tend to “stick” to the surface. These airmolecules in turn impede the motion of adjacent air molecules in the airflow, which in turn impede other air molecules. Thus, a region ofslow-moving air molecules forms over the surface. This region is knownas a velocity boundary layer.

The velocity boundary layer limits the number of air molecules that comeinto contact with the surface. Actual heat transfer only occurs at thissurface. As a result, once heat is transferred to or from the moleculesin the boundary layer, further transfer of heat is largely blocked. Moreheat can only be transferred once the molecules in the boundary layerare dragged away from the surface by the viscosity of the air, which isan intrinsically inefficient process. Molecular collisions also candrive the molecules away from the surface, but this is an even moreinefficient process. As a result, the velocity boundary layer isaccompanied by a thermal boundary layer.

The thermal boundary layer greatly impedes the transfer of heat betweenthe forced air and the substrate, duct or grille. In addition, theforcing elements (e.g., fans) for conventional heat transfer devicesmust be powerful enough to overcome the viscosity of the air. Otherwise,little heat transfer will occur. Because of these factors, heating andcooling units tend to be fairly large devices with large footprints.These large footprints are the limiting design factors in many moderndevices.

One alternative technique that has been explored with little success isheating or cooling the blades of fans that force (i.e., blow) air.However, in this approach, a thermal boundary layer forms on the blades.As a result, this approach is no more efficient than forcing air over orthrough a substrate, duct or grille. All of these problems also existwhen transferring heat to or from any other gas or gas mixture besidesair.

SUMMARY OF THE INVENTION

What is needed is a device or technique that permits heat exchange to orfrom air (or other gaseous matter) substantially without creation ofvelocity and thermal boundary layers.

Accordingly, one aspect of the invention is a method of transferringheat to or from a gas. The method includes the steps of moving a surfacewith sufficient speed to disrupt a velocity boundary layer for moleculesof the gas in contact with the surface, and cooling or heating thesurface. Preferably, the moving step and the heating or cooling stepoccur simultaneously. Cooling results in a transfer of energy from themolecules to the surface, whereas heating results in a transfer ofenergy from the surface to the molecules.

Another aspect of the invention is also a method of transferring heat toor from a gas. This method includes the steps of selecting moleculesfrom the gas using a heteroscopic structure, and heating or cooling atleast part of the heteroscopic structure that comes into contact withthe selected molecules. Cooling results in a transfer of energy from themolecules to the heteroscopic structure, whereas heating results in atransfer of energy from the heteroscopic structure to the molecules.

An embodiment of the invention can perform one or both of these methods.In particular, a velocity boundary layer is unlikely to form on aheteroscopic structure that is moved sufficiently fast to selectsmolecules from a gas.

The gas can be air, and the molecules can be selected from the gas athigher than near-vacuum pressure such as atmospheric pressure.

Preferably, the heteroscopic structure includes microscopic ornanoscopic turbine blades moving at a speed comparable to a mean thermalvelocity of the gas. These turbine blades can feed into microscopic ornanoscopic ducts that are cooled or heated.

In heteroscopic turbine embodiments, the turbine blades can be mountedon or in a rotating structure. Alternatively, the turbine blades can bemounted on or in a linearly moving structure, for example a componentsuch as a radiator of a vehicle that moves through the gas.

Additional aspects of the invention include devices that implement theforegoing methods, as well as other embodiments and features discussedbelow.

This brief summary has been provided so that the nature of the inventionmay be understood quickly. A more complete understanding of theinvention may be obtained by reference to the following description ofthe preferred embodiments thereof in connection with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows transfer of heat to a gas from a surface with an attenuatedor absent velocity boundary layer according to one aspect of theinvention.

FIG. 2 shows transfer of heat from a gas to a surface with an attenuatedor absent velocity boundary layer according to one aspect of theinvention.

FIG. 3 shows a rotational embodiment of one aspect of the invention.

FIG. 4 shows a linearly moving embodiment of one aspect of theinvention.

FIGS. 5 to 8 show embodiments of aspects of the invention that work inconjunction with selection of molecules from a gas, for example by aheteroscopic turbine.

FIG. 9 illustrates transfer of heat to or from a gas in a duct accordingto an aspect of the invention.

FIG. 10 illustrates some possible mounting arrangements for blades for aturbine that can be used in conjunction with aspects of the invention.

FIGS. 11 to 35 illustrate various blade and ducting arrangements thatcan be used in conjunction with aspects of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Lexicography

Nanoscopic: Having lengths or dimensions less than or equal to abillionth of a meter.

Microscopic: Having lengths or dimensions less than or equal to onemillimeter.

Macroscopic: Having lengths or dimensions greater than or equal to onemillimeter, and numbers greater than about one hundred.

Heteroscopic: Characterized by use of microscopic or nanoscopicprinciples to generate macroscopic effects.

Transport speed: The mean speed of an flow of gaseous matter moving inbulk. Also called bulk speed.

Mean thermal velocity: The speed of molecules in gaseous matter.

Mean free path distance: The average distance that molecules in gaseousmatter travel between collisions with other molecules in the gaseousmatter.

Hotter molecules: In reference to a given gas, hotter molecules consistof an aggregation of molecules selected from the gas that have a meanthermal velocity faster than the mean thermal velocity of the gas. Inreference to individual molecules, a so-called hotter molecule isexpected, on average, to be faster and therefore hotter than a so-calledcooler molecule, but exceptions can occur.

Cooler molecules: In reference to a given gas, cooler molecules consistof an aggregation of molecules selected from the gas that have a meanthermal velocity slower than the mean thermal velocity of the gas. Inreference to individual molecules, a so-called cooler molecule isexpected, on average, to be slower and therefore cooler than a so-calledhotter molecule, but exceptions can occur.

Near vacuum conditions: Pressures less than or equal to 0.001atmospheres.

Blade: Broadly, any edge that is moved through air. This termencompasses both flat blades and tops of holes in a moving surface.

Comparable: In this application, speeds and distances are comparable ifthey are within an order of magnitude of each other. For example, if airmolecules have a mean thermal velocity of 500 meters per second, bladesmoving at 50 to 5,000 meters per second would be moving at speedscomparable to the mean thermal velocity of the air molecules. Throughoutthis disclosure, the term “on an order of” is synonymous to “comparableto.”

Boundary Layer Attenuation

FIG. 1 shows transfer of heat to a gas from a surface with an attenuatedor absent velocity boundary layer according to one aspect of theinvention.

In FIG. 1, substrate 1 is being heated by heating element 2, which canbe below, within, otherwise in contact with, or part of substrate 1.This element is shown as a coil, but could be any other type of heatingelement.

A surface of substrate 1 is in contact with a gas. The gas could be butis not limited to air. The invention preferably can operate at higherthan near-vacuum pressure, including at atmospheric pressure.

The arrow in FIG. 1 indicates movement of substrate 1. If this movementis sufficiently fast, velocity and thermal boundary layer 4 will beattenuated or even eliminated.

Thermal motion of molecule 5 can bring the molecule into contact withthe surface more easily than would be possible if a significant boundarylayer was present. Applicant refers to this process as “forcedconduction.”

In FIG. 1, the molecule comes into contact with the surface at energytransfer point 6. Because substrate 1 is heated, the speed (i.e.,thermal velocity) of molecule 5 is increased by the contact. After thisenergy transfer, the molecule has a significant chance of flying off toor even through transport layer 7 for the gas at the surface.

In the absence of a strong boundary layer, a great many molecules canundergo the process described above for molecule 5. As a result, highlyefficient transfer of heat from substrate 1 to the gas is facilitated,thereby heating the gas.

FIG. 2 shows transfer of heat from a gas to a surface with an attenuatedor absent velocity boundary layer according to one aspect of theinvention.

In FIG. 2, substrate 9 is being cooled by cooling element 10, which canbe below, within, otherwise in contact with, or part of substrate 9.This element is shown as a coil, but could be any other type of coolingelement.

A surface of substrate 9 is in contact with a gas. The gas could be butis not limited to air. The invention preferably can operate at higherthan near-vacuum pressure, including at atmospheric pressure.

The arrow in FIG. 2 indicates movement of substrate 9. If this movementis sufficiently fast, velocity and thermal boundary layer 12 will beattenuated or even eliminated.

Thermal motion of molecule 13 can bring the molecule into contact withthe surface more easily than would be possible if a significant boundarylayer was present. Applicant refers to this process as “forcedconduction.”

In FIG. 2, the molecule comes into contact with the surface at energytransfer point 14. Because substrate 9 is cooled, the speed (i.e.,thermal velocity) of molecule 13 is decreased by the contact. Despitebeing slowed, the molecule has a significant chance of flying off to oreven through transport layer 15 for the gas at the surface after theenergy transfer.

In the absence of a strong boundary layer, a great many molecules canundergo the process described above for molecule 13. As a result, highlyefficient transfer of heat from the gas to substrate 9 is facilitated,thereby cooling the gas.

FIG. 3 shows a rotational embodiment of one aspect of the invention. InFIG. 3, a substrate is formed into a rotational surface. Such surfacesinclude, but are not limited to, disks, annular airfoils, and the like.Preferably, the surface is rotated such that it moves at a speedcomparable to a mean thermal velocity of a gas in which the embodimentis intended to operate.

Heating or cooling elements are disposed across the surface, asillustrated by the dashed lines. Thus, energy transfer as describedabove can occur throughout the surface.

In an alternative embodiment, heating or cooling elements arepreferentially disposed near the outside circumference of the surface totake advantage of higher radial velocities. These higher velocities tendto help attenuate or eliminate the boundary layer.

FIG. 4 shows a linearly moving embodiment of one aspect of theinvention.

Preferably, the surface moves at a speed comparable to a mean thermalvelocity of a gas in which the embodiment is intended to operate.

In FIG. 4, heating or cooling elements are disposed across the surfaceof a substrate, as illustrated by the dashed lines. Thus, energytransfer as described above can occur throughout the surface.

In some embodiments, the substrate in FIG. 4 could be a component suchas a radiator of a vehicle that moves through the gas. Other settingsexist in which the linearly moving embodiment could be useful.

Additional Structures

In each of the situations described above, disruption of the boundarylayer can be facilitated by the addition of structures onto the surfaceof the substrate. Preferably, the structures are microscopic ornanoscopic, and a large number of the structures are used. For example,in some embodiments, well over a trillion such structures could besituated on the surface of a substrate according to the invention. Moreor less such structures could be used in different embodiments.

Heteroscopic Devices and Effects

One class of devices that embodies such microscopic or nanoscopicstructures includes heteroscopic turbines. These devices use blades tosegregate molecules from a gas. A bulk flow is then created from thosemolecules.

In more detail, heteroscopic devices operate on two different scales.First, the devices select molecules from a gas on a microscopic ornanoscopic scale. In particular, the structures that select themolecules have dimensions comparable with the mean free path distance ofthe molecules for a gas at a pressure at which the turbine is intendedto operate. In normal operating conditions, for example regularatmospheric pressure, these dimensions are somewhere between microscopicand nanoscopic. The invention is not limited to such operatingconditions.

Second, the devices generate macroscopic effects. For example, thesegregated molecules converge or are directed to generate a bulk flow.The bulk flow can be created from the segregated molecules by thearrangement of the segregating structures, by use of macroscopicstructures such as flow ducts, by some combination of thesearrangements, or by some other structures or techniques.

On an output side, a bulk flow generated by the aggregation of theselected molecules serves to push other ambient molecules out of theway. In systems that do not generate such bulk flows, “infidel”molecules entering from the output side can force the systems to dosignificant extra work. In the invention, the momentum of moleculescomprising the bulk flow pushes would-be infidels away from the outputside, thereby helping to prevent those molecules from colliding with thestructures.

The action of the heteroscopic turbine leads to an attenuated or absentboundary layer at an interface between a gas and the turbine blades. Asa result, a great many molecules can come into contact with thestructures of the turbine and therefore can be selected and aggregatedinto a bulk flow. Preferably, the molecules can be heated or cooled asthey are selected, while being aggregated in the bulk flow, or both,thereby facilitating efficient heating or cooling of those molecules.

The invention is also applicable to heteroscopic devices other thanturbines. For example, blades as described for the turbine could bedisposed across a linearly moving surface such as the one illustrated inFIG. 4.

With the heteroscopic devices, heating or cooling elements can be usedto heat or cool the blades, the substrates on which the blades aremounted or otherwise disposed, any ducting for directing molecular oraggregated (i.e., bulk) flow, and any other parts of the devices. Whenmolecules contact these heated or cooled surfaces, a transfer of energyalters the thermal velocity of the molecules, heating or cooling the gascomprised of the molecules. In the case of the blades, ducting formolecular flow, and some other parts of the devices, the molecularnature of the interaction results in an attenuated or an eliminatedboundary layer, permitting more molecules to interact and therebyhelping to improve efficiency.

FIGS. 5 to 8 show embodiments of aspects of the invention that work inconjunction with selection of molecules from a gas, for example by aheteroscopic turbine.

FIG. 5 shows an example in which molecules of a gas are heated. In FIG.5, blades 20 are mounted on or in substrate 21. Heat is being applied toblades 20, for example through substrate 21. The height and spacing ofthe blades are preferably comparable to a mean free path distance forthe gas in which the device is intended to operate. In one embodiment,the blades are angled in a direction of expected motion, represented byan arrow in FIG. 5.

When blades 20 are in motion, the tops of the blades form directionselection plane 23. When thermal motion of molecules brings them acrossthe direction selection plane, blades 20 will whisk them away. Moleculesthat do not cross direction selection plane 23 do not “stick” to theplane, so little or not boundary layer forms.

Molecule 24 is an example of a molecule that crosses direction selectionplane 23. The molecule strikes one of blades 20 at energy transfer point25. Any point in the device could be such an energy transfer point.

Because the blade is heated, the thermal velocity of molecule 24 isincreased at energy transfer point 25. In other words, energy istransferred from the blade to the molecule. Additional energy transferscould occur. The molecule then passes through an opening or duct (notshown) in substrate 21 to contribute to flow 27.

In the absence of a strong boundary layer, a great many molecules canundergo the process described above for molecule 24. As a result, highlyefficient transfer of heat from the device to the gas is facilitated,thereby heating the gas.

FIG. 6 shows an example in which molecules of a gas are cooled. In FIG.6, blades 30 are mounted on or in substrate 31. Cool is being applied toblades 30, for example through substrate 31. The height and spacing ofthe blades are preferably comparable to a mean free path distance forthe gas in which the device is intended to operate. In one embodiment,the blades are angled in a direction of expected motion, represented byan arrow in FIG. 6.

When blades 30 are in motion, the tops of the blades form directionselection plane 33. When thermal motion of molecules brings them acrossthe direction selection plane, blades 30 will whisk them away. Moleculesthat do not cross direction selection plane 33 do not “stick” to theplane, so little or not boundary layer forms.

Molecule 34 is an example of a molecule that crosses direction selectionplane 33. The molecule strikes one of blades 20 at energy transfer point35. Any point in the device could be such an energy transfer point.

Because the blade is cooled, the thermal velocity of molecule 34 isdecreased. In other words, energy is transferred from the molecule tothe blade. Additional energy transfers could occur. The molecule thenpasses through an opening or duct (not shown) in substrate 31 tocontribute to flow 37.

In the absence of a strong boundary layer, a great many molecules canundergo the process described above for molecule 34. As a result, highlyefficient transfer of heat from the gas to the device is facilitated,thereby cooling the gas.

FIG. 7 shows an example in which molecules of a gas are heated. Thisembodiment is akin to the one shown in FIG. 5, except that blades withdifferent heights are used. Some of the blades are shorter than otherblades.

The shorter blades form speed selection plane 40. Only molecules with asufficiently high thermal velocity (i.e., moving sufficiently fast) willcross the speed selection plane before a shorter blade passes. Thus, theshorter blades tend to capture a hotter subset of molecules.

In FIG. 7, molecule 41 is a hotter molecule that crosses both thedirection selection and the speed selection planes before being capturedby a shorter blade. The molecule strikes one of the blades at energytransfer point 43. Any point in the device could be such an energytransfer point.

Because the blade is heated, the thermal velocity of molecule 41 isincreased at energy transfer point 43. In other words, energy istransferred from the blade to the molecule. Additional energy transferscould occur. The molecule then passes through an opening or duct (notshown) in the substrate to contribute to flow 44.

Cooler molecules could cross the speed selection plane but not becaptured by a shorter blade. Such molecules also could be heated.However, because these molecules start out cooler, heating the moleculesmight be less effective. In some embodiments, such molecules are shuntedtoward a cool exhaust, for example through some form of ducting.

FIG. 8 shows an example in which molecules of a gas are cooled. Thisembodiment is akin to the one shown in FIG. 6, except that blades withdifferent heights are used. Some of the blades are shorter than otherblades.

The shorter blades form speed selection plane 50. Only molecules with asufficiently high thermal velocity (i.e., moving sufficiently fast) willcross the speed selection plane before a shorter blade passes. Thus, theshorter blades tend to capture a hotter subset of molecules.

In FIG. 8, molecule 51 is a cooler molecule that does not cross thespeed selection plane in time to be captured by a shorter blade. Themolecule strikes one of the blades at energy transfer point 53. Anypoint in the device could be such an energy transfer point.

Because the blade is cooled, the thermal velocity of molecule 51 isdecreased at energy transfer point 53. In other words, energy istransferred from the molecule to the blade. Additional energy transferscould occur. The molecule then passes through an opening or duct (notshown) in the substrate to contribute to flow 54.

Hotter molecules could cross both the direction selection and the speedselection planes before being captured by a shorter blade. Suchmolecules also could be cooled. However, because these molecules startout hotter, cooling the molecules might be less effective. In someembodiments, such molecules are shunted toward a hot exhaust, forexample through some form of ducting.

FIG. 9 illustrates transfer of heat to or from a gas in a duct accordingto an aspect of the invention. Ducting can be used to transportmolecules that have been selected by blades such as those illustratedherein.

The ducting could be small enough (e.g., on an order of a mean from pathdistance) so that only molecular flow occurs within it. In such a case,little or not boundary layer can form on the sides of the duct. Thus,molecules that pass through the duct can easily strike the sides of theduct, for example at energy transfer point 60. When a molecule strikesthe duct, energy could be transferred to for from the molecule,depending on if the duct is heated or cooled.

Alternatively, the duct could be a macroscopic duct. In such a case, aboundary layer could form on the sides of the duct. Alternatively, ifthe flow through the duct is sufficiently fast, the boundary layer couldbe absent or attenuated. In either case, energy transfers to moleculesthat collide with the sides of the duct could occur, although more arelikely to occur if the boundary layer is absent or attenuated.

FIG. 10 illustrates some possible mounting arrangements for blades for aturbine that can be used in conjunction with aspects of the invention.FIG. 10 shows an annulus with two different mounting arrangements. Thesearrangements could be used separately, in conjunction, or in conjunctionwith other mounting arrangements.

One arrangement is illustrated with dashed curved lines 62. These linesrepresent blades mounted all over the surface of the edge of theannulus. The advantage of this arrangement is that a great many bladescan be packed onto the surface with little wasted space.

The other arrangement is illustrated with small circles 64. Thesecircles represent chips manufactured with the blades. The advantage ofthis arrangement is that the smaller chips can be easier to manufacture.In addition, a manufacturing defect in a chip ruins only that chip,which preferably can be replaced.

Preferably, the annulus rotates such that the mounted blades move at aspeed comparable to a mean thermal velocity of a gas in which theembodiment is intended to operate.

One possible embodiment of the annulus has a circumference of 4 metersand rotates at 7,500 RPM. Somewhere on the order of 1.75E+13 such bladescould easily by placed on the annulus, which could be heated or cooledas desired. This would result in a significant flow of heated or cooledgas exiting the annulus. Of course, the invention is not limited in anyway to these particular numerical examples.

FIG. 10 also illustrates conventions for “radial view” and “tangentialview” that are used in some of the illustrations in FIGS. 11 to 35. Evenwhere these conventions are noted in those figures, the structures shownin FIGS. 11 to 35 are equally applicable to linearly moving embodimentsof the invention.

FIGS. 11 to 35 illustrate various blade and ducting arrangements thatcan be used in conjunction with aspects of the invention. Each of thesestructures can be used with the devices and techniques described above.

Alternative Embodiments

Although preferred embodiments of the invention are disclosed herein,many variations are possible which remain within the content, scope andspirit of the invention, and these variations would become clear tothose skilled in the art after perusal of this application.

1. A method of transferring heat to or from a gas, comprising the stepsof: moving a rotating surface with sufficient speed to disrupt avelocity boundary layer for molecules of the gas in contact with thesurface; and cooling or heating the surface; wherein cooling results ina transfer of energy from the molecules to the surface, and heatingresults in a transfer of energy from the surface to the molecules.
 2. Amethod as in claim 1, wherein the moving step and the heating or coolingstep occur simultaneously.
 3. A method as in claim 1, wherein the gas isair.
 4. A method as in claim 1, wherein at least part of the rotatingsurface moves at a speed comparable to a mean thermal velocity of thegas.
 5. A method of transferring heat to or from a gas, comprising thesteps of: selecting molecules from the gas using a heteroscopicstructure; and heating or cooling at least part of the heteroscopicstructure that comes into contact with the selected molecules; whereincooling results in a transfer of energy from the molecules to theheteroscopic structure, and heating results in a transfer of energy fromthe heteroscopic structure to the molecules.
 6. A method as in claim 5,wherein the selecting step and the heating or cooling step occursimultaneously.
 7. A method as in claim 5, wherein the gas is air.
 8. Amethod as in claim 5, wherein the molecules are selected from the gas athigher than near-vacuum pressure.
 9. A method as in claim 8, wherein themolecules are selected from the gas at atmospheric pressure.
 10. Amethod as in claim 5, wherein the heteroscopic structure includesmicroscopic or nanoscopic turbine blades moving at a speed comparable toa mean thermal velocity of the gas.
 11. A method as in claim 10, whereinthe turbine blades feed into microscopic or nanoscopic ducts that arecooled or heated.
 12. A method as in claim 10, wherein the turbineblades are mounted on or in a rotating structure.
 13. A method as inclaim 10, wherein the turbine blades are mounted on or in a linearlymoving structure.
 14. A method as in claim 13, wherein the linearlymoving structure is a component of a vehicle that moves through the gas.15. A method as in claim 14, wherein the component is a radiator.
 16. Adevice that transfers heat to or from a gas, comprising: a rotatingsurface moved with sufficient speed to disrupt a velocity boundary layerfor molecules of the gas in contact with the surface; and cooling orheating elements that cool or heat the surface; wherein cooling resultsin a transfer of energy from the molecules to the surface, and heatingresults in a transfer of energy from the surface to the molecules.
 17. Adevice as in claim 16, wherein the gas is air.
 18. A device as in claim16, wherein at least part of the rotating surface moves at a speedcomparable to a mean thermal velocity of the gas.
 19. A device thattransfers heat to or from a gas, comprising: a heteroscopic structurethat selects molecules from the gas; and cooling or heating elementsthat cool or heat at least part of the heteroscopic structure that comesinto contact with the selected molecules; wherein cooling results in atransfer of energy from the molecules to the heteroscopic structure, andheating results in a transfer of energy from the heteroscopic structureto the molecules.
 20. A device as in claim 19, wherein the gas is air.21. A device as in claim 19, wherein the molecules are selected from thegas at higher than near-vacuum pressure.
 22. A device as in claim 21,wherein the molecules are selected from the gas at atmospheric pressure.23. A device as in claim 19, wherein the heteroscopic structure includesmicroscopic or nanoscopic turbine blades moving at a speed comparable toa mean thermal velocity of the gas.
 24. A device as in claim 23, whereinthe turbine blades feed into microscopic or nanoscopic ducts that arecooled or heated.
 25. A device as in claim 23, wherein the turbineblades are mounted on or in a rotating structure.
 26. A device as inclaim 23, wherein the turbine blades are mounted on or in a linearlymoving structure.
 27. A device as in claim 26, wherein the linearlymoving structure is a component of a vehicle that moves through the gas.28. A device as in claim 27, wherein the component is a radiator.